TOLEDO, Ohio (AP) — Smoking cigarettes or burning candles started a mobile home fire that killed five young children and their mother’s boyfriend, investigators said Friday.

The cause of the fatal fire was officially listed as undetermined, but evidence found where it started pointed to the source, Tiffin fire Chief William Ennis Jr. said.

“We can’t tell you exactly whether it was a candle or a cigarette, but it was one of those two, we’re certain,” he said.

The investigation also determined there were working smoke detectors inside the mobile home and firefighters could hear the alarms going off when they forced their way into it.

The children, ages 1 to 6, and the man died early Sunday morning in Tiffin, a city in northwestern Ohio. The children’s mother, Anna Angel, was working at her fast-food job when the fire broke out.

Angel’s four daughters, ages 3, 4, 5 and 6, were laid to rest in a casket following their funeral on Thursday. Her son, 1, was buried with his father, the man who died in the fire.

The fire swept through the mobile home quickly, breaking out windows and peeling some of the home’s aluminum siding, while neighbors watched helplessly as firefighters found the bodies of the children.

There was heavy fire in the center of the mobile home and heavy smoke throughout it when firefighters arrived.

The four girls were found in a bedroom and hallway near the back of the trailer while the boy was under a pile of clothes near where his father was discovered, an investigation report released Friday said.

Investigators believe the man, Timothy Fresch, picked up his son and was trying to get out of the mobile home, Ennis said.

“Our feeling was that by the time he got him, the fire grew so fast he had no way to get out,” Ennis said. “That was the same with the girls.”

There was nothing to indicate that anything criminal took place, the report said.

Organizers of a fund to help Angel pay for the funerals and other expenses raised about $16,000 within two days of the fire. Rappers The Game and Drake pledged to donate another $22,500 after hearing about what happened.